Microvasculature in Angiotensin II–Dependent Cardiac Hypertrophy in the Rat

—The long-lasting effect of angiotensin II (Ang II) on the microvasculature in the rat left ventricle was studied. Immunolabeling of ventricular cryosections combined with morphometric analysis allowed us to (1) distinguish between capillaries and arterioles and (2) precisely evaluate their respective densities in the endomyocardium. Ang II–induced hypertensive cardiac hypertrophy was associated with an 18% decrease in capillary density (P <0.05) and an increase in arteriole density (+54%,P <0.001). Treatments with losartan orPD123319 , the respective antagonists of the angiotensin subtype 1 and subtype 2 receptors, prevented the increase in arteriolar density, whereas only losartan, which restored normal arterial pressure, prevented changes in capillary density. Taken together, these results indicate that Ang II–induced cardiac hypertrophy was associated with capillary rarefaction and arteriolar growth, the 2 processes being independently regulated.